LITHIUM IN THE SUBSOIL OF UKRAINE Part 11. Mineralogical criteria for prospecting and evaluation of lithium-bearing objects: chamber pegmatites

Chamber pegmatites prospecting and evaluation criteria based on quartz, micas and feldspars mineralogical features have been formed. Productivity (ore content) mineralogical criteria assessing based on new X-ray and spectroscopic data, are a significant addition to previously developed criteria: 1. According to theory productive pegmatites, should be fully differentiated bodies. 2. Fully differentiated pegmatites contain alkali feldspars with high and maximum values of ordering (t1) and triclinicity (Δр) and a minimum content of the monoclinic phase in early zones. Bodies, containing mainly monoclinic feldspar at the graphic and pegmatoid zones, are unproductive. Pegmatites high differentiation positive indicator is a sharp but monotonic change in Δp and the content of the monoclinic phase from outer to inner part of the pegmatite. Negative indicator of productivity reflecting the initial heterogeneity of the substance are instability of the alkali feldspars parameters within one zone, sharp discrepancies of these values without a noticeable tendency to decrease in the inner part of the body. 3. Pegmatite is most likely promising on raw crystal material if it is possible to identify all alkali feldspar crystals morphological types. 4. Quartz, topaz, beryl and Li-Fe micas giant crystals growth precondition in the intrusions was the long-term influx of deep fluids into the intrusions — products of degassing of magma of acidic and base composition. 5. The higher the average NH3+ content and the lower the K/NH3+-ratio of feldspar, the more promising the pegmatite is for raw crystal. 6. T-centers in microclines are inversely correlated with the number of F-centers, so the ratio of T/F-centers is convenient to use for assessing pegmatites of all formational types. 7. The highest concentrations of Al-Li-centers in quartz increase at the series: muscovite-crystalline-rare metal pegmatites. 8. Thermo- and X-ray luminescence (TL and RL) of whitish micas could be used as a criterion for assessing the productivity of pegmatites. 9. Thermobarogeochemical criteria — general gasometric, endocarbonic acid, organic geochemical — are of great practical importance for assessing the productivity of chamber pegmatites. In particular, productive pegmatites differ from unproductive ones by their increased water content, amount of gases, and presence of organic compounds.